title: Epoxy-based hydrogels investigated by high-frequency dielectric relaxation spectroscopy.
abstract: Using high-frequency dielectric relaxation spectroscopy, nanophase-separated structures of epoxy-based hydrogels were investigated as a function of water content at 25 °C. The dielectric spectra resulting from the hydrogels were reasonably decomposed into two Debye-type and two Cole-Cole-type relaxation modes. The fastest Debye-type mode, found at 8.3 ps, was attributed to the rotational relaxation process of free water molecules in the bulk state. The other Debye-type mode, at ca. 20-34 ps, originates from the exchange process of water molecules that are hydrogen-bonded to the hydrophilic epoxy network portions for free bulk ones. The first Cole-Cole-type mode observed, at ca. 20-370 ps, was assigned to the complicated dynamics for electric dipole moments of the hydrophilic groups in the epoxy networks (mainly monomeric oxyethylene units). The slowest major Cole-Cole-type mode, at 5-29 ns, was attributed to the Maxwell-Wagner-Sillars polarization process and confirmed the presence of the nanophase-separated structures as revealed by the previous small-angle neutron scattering experiments.
authors.affiliation: Department of Macromolecular Physics, Faculty of Mathematics and Physics, Charles University , V Holešovičkách 2, 180 00 Prague 8, Czech Republic.
authors.forename: Ivan
authors.initials: I
authors.lastname: Krakovský
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Shikata
authors.forename: Ryuta
authors.initials: R
authors.lastname: Hasegawa